\begin{tikzpicture}[parent anchor=east,child anchor=west,grow=east,sibling distance=15mm,level distance=15mm,every node/.style={ball color=cyan,circle,text=black},edge from parent/.style={draw,dashed,thick,red}]
\node {root}
child {node {左节点}}
child {node{右节点}
  child {node {左子}}
  child {node {右子}}
};
\end{tikzpicture}
